The researchers used a version of Mary Ainsworth's 'strange situation test' to assess infants reactions to being separated from their mothers. Children who were placed in day care for at least 20 hours per week while under the age of 1, for a four month period or longer, were compared to children looked after at home. 43% of day care children were found to show insecure attachments on comparison to 26% among those who were home-reared.
A limitation of the study is that it does not take account of parenting differences or pre-existing differences between the two samples. Furthermore, the strange situation may not be an accurate research tool in this context, as children in day care are more used to being separated, and may be indifferent to being left. This could result in their being incorrectly categorised as 'insecure-avoidant'.
Most reviews such as Durkin (1995) have found minimal negative effects of early day care. However, Belsky & Rovine's study is evidence that early separations should be approached with caution.
Belsky, J. and Rovine, M.J. (1988). Non-maternal care in the first year of life and the infant-parent attachment. Child Development, 59, 157-167.
